Find the incorrect term in the following number series. Series: 5, 10, 40, 80, 320, 550, 2560

Introduction / Context:
This problem checks recognition of an alternating multiplication pattern. Detecting a simple repeat like ×2, ×4, ×2, ×4 … allows you to identify the misfit quickly.

Given Data / Assumptions:

• Series: 5, 10, 40, 80, 320, 550, 2560
• We suspect alternating multipliers.
• Exactly one term is wrong (the “odd one out”).

Concept / Approach:
Test an alternating scheme: multiply by 2, then by 4, repeating. If one term fails this scheme, it is the incorrect entry.

Step-by-Step Solution:
5 × 2 = 10 ✓ 10 × 4 = 40 ✓ 40 × 2 = 80 ✓ 80 × 4 = 320 ✓ 320 × 2 = 640 (but the series shows 550 ✗) Continuing the rule would give 640 × 4 = 2560 (which matches the last term).

Verification / Alternative check:
Replacing 550 by 640 makes the entire sequence consistent with ×2, ×4 repetition.

Why Other Options Are Wrong:
80, 320, 2560 all satisfy the alternating multiplication rule with their neighbors.

Common Pitfalls:
Overlooking the alternating nature and searching for a single fixed multiplier.

Final Answer:
550